Not Applicable.
Not Applicable.
The present invention relates generally to quantitative ultrasound equipment and in particular, to an ultrasonic transducer providing separate transmission modes for imaging and quantitative measurement.
Quantitative ultrasound may be used to make measurements of in vivo tissue. In one such device used to assess bone quality, in evaluating conditions such as osteoporosis, an opposed ultrasonic transmitter and ultrasonic receiver are positioned across a body member containing trabecular bone. The heel is often the site of measurement because of its ready accessibility, the relatively thin layers of soft tissue surrounding it, and because the heel bone or os calcis is in significant proportion trabecular bone.
The ultrasonic signal after passing through the bone and soft tissue is analyzed to assess bone health. The analysis may determine changes in sound speed, attenuation, or other parameters. One such system is described in U.S. Pat. No. 6,027,449, entitled: xe2x80x9cUltrasonometer Employing Distensible Membranesxe2x80x9d. This patent is assigned to the assignee of the present case and is hereby incorporated by reference.
While the earliest quantitative ultrasound devices for bone measurement were limited to providing quantitative output, it was recognized that the ability to provide an image could be useful in positioning the body member and therefore in obtaining reproducible results in measurements separated over time. Ultrasonic images may be obtained by scanning a single receiving transducer or by dividing an ultrasonic receiver into a number of elements arranged in an array and separately detecting the received ultrasonic signal at each element. The present invention to be described below is applicable to both techniques.
The separate measurements are analyzed as to speed of sound, or attenuation or another parameter and these analyzed values are mapped to a gray scale and used to produce an image with each gray scale value placed in a picture location (pixel) corresponding to the point of detection of the original ultrasonic signal. The image may be displayed and/or used in an automatic method for identifying a region of interest for quantitative measurement.
The present inventors have recognized that multi-path interference from ultrasound coming around the bone compromises the quantitative analysis of the ultrasound waves coming through the bone. This xe2x80x9caround-the-bonexe2x80x9d component increases with the larger sized ultrasonic transmitter necessary to fully xe2x80x9cilluminatexe2x80x9d the bone for imaging purposes.
Once the interference reaches the ultrasonic receiver, it is difficult to remove or compensate for its influence. Accordingly, the present invention provides a dual mode ultrasonic transmitter that provides first, small-area, ultrasonic transmitter which produces a localized source of ultrasonic energy for quantitative measurements, and second a larger ultrasonic transducer, used in conjunction with the smaller ultrasonic transducer which produces a large area ultrasonic wave suitable for imaging the bone and the surrounding tissue. These two modes are used as required.
Specifically then, the present invention provides an imaging/quantitative ultrasonic device having an ultrasonic receiver unit providing a reception aperture of a first predetermined area and an ultrasonic transmission unit having a transmission aperture of a second predetermined area, the ultrasonic transmission unit positioned in opposition across a measurement region from the ultrasonic receiver unit for directing ultrasonic acoustic waves to the reception aperture. The ultrasonic transmission unit further includes a means for independently transmitting ultrasonic acoustic waves from a first and second portion of the transmission aperture. A controller communicates with the ultrasonic transmission unit to alternately transmit ultrasonic waves from (a) only the first of the transmission aperture for preparing a quantitative measurement, and (b) both the first and second portions of the transmission aperture for preparing an image.
In this way, scattered ultrasound coming around the bone may be minimized in the quantitative measurement while still providing a uniform broad area ultrasonic signal for imaging purposes.
The ultrasonic transmission unit may have an electrically separate circular transducer and a coaxially annular transducer.
Thus, the present invention is well adapted to use of standard ceramic transducer technologies.
The first transducer may have a diameter of substantially one inch.
In this way, the transducer can be constructed to match the existing ultrasonic densitometry equipment and provide consistent measurement with other machines.
The ultrasonic receiver may include an array of receiving elements and the controller may communicate with the receiver unit to sequentially (a) detect ultrasonic acoustic waves from only a first portion of the reception aperture when the ultrasonic acoustic waves are being transmitted only from the first portion of the transmission aperture and (b) detect ultrasonic acoustic waves from both the first and the second portion of the reception aperture when the ultrasonic acoustic waves are being transmitted from both the first and second portions of the transmission aperture.
In this way, the receiver can also be used to discriminate between direct and scattered ultrasound.
The ultrasonic transmission unit and ultrasonic receiver unit may be separated by a distance less than twice the diameter of the reception and transmission apertures.
Such a separation ensures that a generally planar acoustic wave may be generated for imaging purposes.
The foregoing features and advantages may not apply to all embodiments of the inventions and are not intended to define the scope of the invention for which purpose claims are provided. In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration, a preferred embodiment of the invention. Such embodiment also does not define the scope of the invention and reference must be made therefore to the claims for this purpose.